Competition and coexistence of bond and charge orders in (TMTTF)2AsF6 -: art. no. 081103

(TMTTF)(2)AsF6 undergoes two phase transitions upon cooling from 300 K. At T-CO=103 K a charge ordering (CO) occurs, and at T-SP(B=9 T)=11 K the material undergoes a spin-Peierls transition. Within the intermediate, CO phase, the charge disproportionation ratio is found to be at least 3:1 from C-13 NMR T-1(-1) measurements on spin-labeled samples. Above T-SP up to about 3T(SP) T-1(-1) is independent of temperature, indicative of low-dimensional magnetic correlations. With the application of about 0.15 GPa pressure, T-SP increases substantially, while T-CO is rapidly suppressed, demonstrating that the two orders are competing. The experiments are compared to results obtained from calculations on the one-dimensional extended Peierls-Hubbard model.